1. Field of the Invention
The invention relates to a running gear for a rail vehicle, in particular a high speed rail vehicle, comprising a wheel set, a running gear frame and a shielding device, the running gear frame being supported on the wheel set. The shielding device is connected to the running gear frame via a support structure and is spatially associated to at least a shielded component of the running gear. The shielding device shields a shielded part of said shielded component of the running gear against impacts of objects, in particular pieces of ballast, lifted from a track used during operation of the vehicle. The shielding device comprises a carrier element and at least one impact element, the at least one impact element being mounted to the carrier element for covering the carrier element and forming an impact surface for said objects.
2. Description of Related Art
Rail vehicles running at high speeds, e.g. at operating speeds beyond 180 km/h or more, often face the problem that, e.g. due to the air flow conditions developing on the underside of the vehicle, typically, in combination with certain adverse events or circumstances, loose objects such as, for example, loose pieces of ballast are lifted from the part of the track currently used (i.e. travelled along) and hit components of the vehicle, in particular, components of the running gear.
Such objects, depending on their relative speed with respect to the vehicle, may not only damage the vehicle components they hit. They may also be further accelerated and reflected back down onto the track bed where their considerably increased kinetic energy eventually causes one or more other objects, typically pieces of ballast, to be lifted up and hit the vehicle. In summary, this may lead to an avalanche effect also referred to as ballast flight with a greatly increased number of pieces of ballast hitting the vehicle underside components in the rear part of a train. Such ballast flight situations may not only lead to a considerable damage to the vehicle. The track and its surroundings may also be heavily affected.
In order to avoid such ballast flight situations it has been suggested in U.S. Pat. No. 7,605,690 B2 (the entire disclosure of which is incorporated herein by reference) to acoustically detect the build up of ballast flight at an early stage, provide a corresponding signal (e.g. to the driver or a vehicle control) and to take appropriate countermeasures such as reducing the speed of the vehicle. However, in particular, on explicit high speed lines, reduction of the operating speed of the vehicle typically is highly undesired. Furthermore, these countermeasures may only become effective after a certain number of impacts and the associated damage to the components hit had already occurred.
As an approach to deal with the vehicle related part of the ballast flight problem it is known to provide protective coatings to the affected vehicle components (e.g. according to EN 13261). However, these coatings, e.g. made of synthetic materials such as polyurethane (PU), are not suited to withstand the high impact loads occurring at very high operating speeds for an appropriate amount of time and, furthermore, require extensive maintenance work (in particular, if directly coated onto the surface of the respective vehicle component). Furthermore, they are not suitable to solve the ballast flight related problems on the track side.
A further approach to deal at least with parts of the ballast flight problem has been suggested in WO 2006/021514 A1 (the entire disclosure of which is incorporated herein by reference). This document discloses a generic running gear for a rail vehicle wherein so called deflector elements are provided. These deflector elements are intended to form a shield protecting components of the vehicle from being hit by such objects lifted up from the track. The generally plate shaped deflector elements, at least in the sections prone to be hit, are explicitly designed to have a very low inclination with respect to the longitudinal direction of the running gear (i.e. the driving direction of the vehicle) to largely avoid any transfer of kinetic energy from the vehicle to the hitting object, which otherwise would be likely to cause the avalanche effect as outlined above.
However, this low inclination of the relevant impact parts of the deflector elements with respect to the longitudinal direction of the running gear results in a very large size of these deflector elements. More precisely, for example, in total, virtually the entire underside of the running gear ahead of a wheel set shaft (including the gap between the wagon body and the bogie in the area of the bogie cutout) has to be shielded in order to protect the wheel set shaft. Such large shielding devices, however, considerably add to the complexity of the running gear. Furthermore, integration of such large shields in a modern high speed running gear (typically having very little free building space available) requires considerable constructional effort.
A similar deflector element approach is known from EP 0 050 200 A1 disclosing generally U-shaped covers for underfloor vehicle components. These self-carrying covers are made of fiber reinforced composite material walls extending substantially parallel to the longitudinal direction, such that they are only exposed to comparatively low impact loads.
Contrary to that DE 10 2006 004 814 A1 discloses a shielding device with a substantially vertical arrangement absorbing ballast impact loads via a ballast impact surface formed by a wire mesh element prone to local damage of individual wires hit by a piece of ballast.
Furthermore, EP 2 517 944 A2 discloses a generic running gear where the shielding device comprises impact energy absorbing elements comprising a wood material as an impact energy absorbing material covering the carrier element. The wood material, while providing good and long term energy absorption, has the disadvantage that it has a comparatively high tendency to absorb water or other liquids going along with a corresponding swelling of the impact element compared to its dried state. This leads to problems or increased efforts, respectively, in mounting the impact element in a long term stable manner despite its strongly and periodically altering geometry over time. A further problem with such a wood material is the general low resistance to fire, such that appropriate additional measures have to be taken to improve fire resistance of the wood material in order to respect operator standards or official regulations regarding fire safety.